Abstract
A new device is proposed which simulates an acoustic inductor using active elements. The sound pressure at a certain point is picked up by a microphone. The medium there is vibrated by an piston at such a velocity as the medium should vibrate if there were a pipe. There is no difference between two cases from the acoustical point of view; the case the medium is vibrated by a piston and the case the medium within a real pipe is vibrating. A trial device was built which employed an electret microphone for picking up the sound pressure and a piezoelectric acuator for vibrating a piston. An experiment of the measurement of cavity capacity was performed with this device. The device was mounted on a container with an empty capacity of 62×10-6m3 to form an acoustic resonator. The capacity of the cavity was varied by filling with water and the resonant frequencies were measured. The reuslts show that the trial device, although the actual dimension of the device is 12mm in diameter and 70mm in length, acts as an acoustic pipe with a length of 1200mm. Finally, the possibility of application of the simulated inductor to the measurement of other quantities is dicussed.
